There’s no question that prosecutor Jennifer Hickman, who is heading up the investigation for Suffolk County District Attorney Daniel F. Conley, will use the grand jury this month to get a DNA sample from Markoff.

Prosecutors will then compare Markoff’s sample with any DNA recovered from the two hotel room crime scenes in the case.

Markoff, who was being held without bail at today’s arraignment, is due back in Boston Municipal Court on May 21.

It sounds like the grand jury has already done a fair amount of work in the case. We should have a better sense on the 21st with regard to when the grand jury will conclude its investigation.